[v3,1/3] rtl: directly handle MEM in gen_highpart [PR102125]

Message ID 20210910144841.3139174-2-rearnsha@arm.com
State New
Headers show
Series
  • lower more cases of memcpy [PR102125]
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Commit Message

Richard Biener via Gcc-patches Sept. 10, 2021, 2:48 p.m.
gen_lowpart_general handles forming a lowpart of a MEM by using
adjust_address to rework and validate a new version of the MEM.
Do the same for gen_highpart rather than calling simplify_gen_subreg
for this case.

gcc/ChangeLog:

	PR target/102125
	* emit-rtl.c (gen_highpart): Use adjust_address to handle
	MEM rather than calling simplify_gen_subreg.
---
 gcc/emit-rtl.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

Comments

Richard Biener via Gcc-patches Sept. 13, 2021, 9:38 a.m. | #1
On Fri, Sep 10, 2021 at 4:48 PM Richard Earnshaw <rearnsha@arm.com> wrote:
>

>

> gen_lowpart_general handles forming a lowpart of a MEM by using

> adjust_address to rework and validate a new version of the MEM.

> Do the same for gen_highpart rather than calling simplify_gen_subreg

> for this case.


OK from my side.

Thanks,
Richard.

> gcc/ChangeLog:

>

>         PR target/102125

>         * emit-rtl.c (gen_highpart): Use adjust_address to handle

>         MEM rather than calling simplify_gen_subreg.

> ---

>  gcc/emit-rtl.c | 23 +++++++++++++----------

>  1 file changed, 13 insertions(+), 10 deletions(-)

>
Richard Biener via Gcc-patches Sept. 13, 2021, 9:38 a.m. | #2
Richard Earnshaw via Gcc-patches <gcc-patches@gcc.gnu.org> writes:
> gen_lowpart_general handles forming a lowpart of a MEM by using

> adjust_address to rework and validate a new version of the MEM.

> Do the same for gen_highpart rather than calling simplify_gen_subreg

> for this case.


Looks OK, but what went wrong with the existing code?  Did
simplify_gen_subreg refuse to handle a MEM that you wanted
it to handle, or did the validize_mem go wrong for some reason?

Thanks,
Richard

> gcc/ChangeLog:

>

> 	PR target/102125

> 	* emit-rtl.c (gen_highpart): Use adjust_address to handle

> 	MEM rather than calling simplify_gen_subreg.

> ---

>  gcc/emit-rtl.c | 23 +++++++++++++----------

>  1 file changed, 13 insertions(+), 10 deletions(-)

>

> diff --git a/gcc/emit-rtl.c b/gcc/emit-rtl.c

> index 77ea8948ee8..0ba110879aa 100644

> --- a/gcc/emit-rtl.c

> +++ b/gcc/emit-rtl.c

> @@ -1585,19 +1585,22 @@ gen_highpart (machine_mode mode, rtx x)

>    gcc_assert (known_le (msize, (unsigned int) UNITS_PER_WORD)

>  	      || known_eq (msize, GET_MODE_UNIT_SIZE (GET_MODE (x))));

>  

> -  result = simplify_gen_subreg (mode, x, GET_MODE (x),

> -				subreg_highpart_offset (mode, GET_MODE (x)));

> -  gcc_assert (result);

> -

> -  /* simplify_gen_subreg is not guaranteed to return a valid operand for

> -     the target if we have a MEM.  gen_highpart must return a valid operand,

> -     emitting code if necessary to do so.  */

> -  if (MEM_P (result))

> +  /* gen_lowpart_common handles a lot of special cases due to needing to handle

> +     paradoxical subregs; it only calls simplify_gen_subreg when certain that

> +     it will produce something meaningful.  The only case we need to handle

> +     specially here is MEM.  */

> +  if (MEM_P (x))

>      {

> -      result = validize_mem (result);

> -      gcc_assert (result);

> +      poly_int64 offset = subreg_highpart_offset (mode, GET_MODE (x));

> +      return adjust_address (x, mode, offset);

>      }

>  

> +  result = simplify_gen_subreg (mode, x, GET_MODE (x),

> +				subreg_highpart_offset (mode, GET_MODE (x)));

> +  /* Since we handle MEM directly above, we should never get a MEM back

> +     from simplify_gen_subreg.  */

> +  gcc_assert (result && !MEM_P (result));

> +

>    return result;

>  }

>
Richard Biener via Gcc-patches Sept. 13, 2021, 9:51 a.m. | #3
On 13/09/2021 10:38, Richard Sandiford via Gcc-patches wrote:
> Richard Earnshaw via Gcc-patches <gcc-patches@gcc.gnu.org> writes:

>> gen_lowpart_general handles forming a lowpart of a MEM by using

>> adjust_address to rework and validate a new version of the MEM.

>> Do the same for gen_highpart rather than calling simplify_gen_subreg

>> for this case.

> 

> Looks OK, but what went wrong with the existing code?  Did

> simplify_gen_subreg refuse to handle a MEM that you wanted

> it to handle, or did the validize_mem go wrong for some reason?


It refused to handle it and simply returned (subreg (mem)) - see the 
discussion on version 1 of the patch series.

R.

> 

> Thanks,

> Richard

> 

>> gcc/ChangeLog:

>>

>> 	PR target/102125

>> 	* emit-rtl.c (gen_highpart): Use adjust_address to handle

>> 	MEM rather than calling simplify_gen_subreg.

>> ---

>>   gcc/emit-rtl.c | 23 +++++++++++++----------

>>   1 file changed, 13 insertions(+), 10 deletions(-)

>>

>> diff --git a/gcc/emit-rtl.c b/gcc/emit-rtl.c

>> index 77ea8948ee8..0ba110879aa 100644

>> --- a/gcc/emit-rtl.c

>> +++ b/gcc/emit-rtl.c

>> @@ -1585,19 +1585,22 @@ gen_highpart (machine_mode mode, rtx x)

>>     gcc_assert (known_le (msize, (unsigned int) UNITS_PER_WORD)

>>   	      || known_eq (msize, GET_MODE_UNIT_SIZE (GET_MODE (x))));

>>   

>> -  result = simplify_gen_subreg (mode, x, GET_MODE (x),

>> -				subreg_highpart_offset (mode, GET_MODE (x)));

>> -  gcc_assert (result);

>> -

>> -  /* simplify_gen_subreg is not guaranteed to return a valid operand for

>> -     the target if we have a MEM.  gen_highpart must return a valid operand,

>> -     emitting code if necessary to do so.  */

>> -  if (MEM_P (result))

>> +  /* gen_lowpart_common handles a lot of special cases due to needing to handle

>> +     paradoxical subregs; it only calls simplify_gen_subreg when certain that

>> +     it will produce something meaningful.  The only case we need to handle

>> +     specially here is MEM.  */

>> +  if (MEM_P (x))

>>       {

>> -      result = validize_mem (result);

>> -      gcc_assert (result);

>> +      poly_int64 offset = subreg_highpart_offset (mode, GET_MODE (x));

>> +      return adjust_address (x, mode, offset);

>>       }

>>   

>> +  result = simplify_gen_subreg (mode, x, GET_MODE (x),

>> +				subreg_highpart_offset (mode, GET_MODE (x)));

>> +  /* Since we handle MEM directly above, we should never get a MEM back

>> +     from simplify_gen_subreg.  */

>> +  gcc_assert (result && !MEM_P (result));

>> +

>>     return result;

>>   }

>>
Richard Biener via Gcc-patches Sept. 13, 2021, 9:54 a.m. | #4
Richard Earnshaw <Richard.Earnshaw@foss.arm.com> writes:
> On 13/09/2021 10:38, Richard Sandiford via Gcc-patches wrote:

>> Richard Earnshaw via Gcc-patches <gcc-patches@gcc.gnu.org> writes:

>>> gen_lowpart_general handles forming a lowpart of a MEM by using

>>> adjust_address to rework and validate a new version of the MEM.

>>> Do the same for gen_highpart rather than calling simplify_gen_subreg

>>> for this case.

>> 

>> Looks OK, but what went wrong with the existing code?  Did

>> simplify_gen_subreg refuse to handle a MEM that you wanted

>> it to handle, or did the validize_mem go wrong for some reason?

>

> It refused to handle it and simply returned (subreg (mem)) - see the 

> discussion on version 1 of the patch series.


OK, that's good then.  The patch is OK from my POV too FWIW.

Richard

>>> gcc/ChangeLog:

>>>

>>> 	PR target/102125

>>> 	* emit-rtl.c (gen_highpart): Use adjust_address to handle

>>> 	MEM rather than calling simplify_gen_subreg.

>>> ---

>>>   gcc/emit-rtl.c | 23 +++++++++++++----------

>>>   1 file changed, 13 insertions(+), 10 deletions(-)

>>>

>>> diff --git a/gcc/emit-rtl.c b/gcc/emit-rtl.c

>>> index 77ea8948ee8..0ba110879aa 100644

>>> --- a/gcc/emit-rtl.c

>>> +++ b/gcc/emit-rtl.c

>>> @@ -1585,19 +1585,22 @@ gen_highpart (machine_mode mode, rtx x)

>>>     gcc_assert (known_le (msize, (unsigned int) UNITS_PER_WORD)

>>>   	      || known_eq (msize, GET_MODE_UNIT_SIZE (GET_MODE (x))));

>>>   

>>> -  result = simplify_gen_subreg (mode, x, GET_MODE (x),

>>> -				subreg_highpart_offset (mode, GET_MODE (x)));

>>> -  gcc_assert (result);

>>> -

>>> -  /* simplify_gen_subreg is not guaranteed to return a valid operand for

>>> -     the target if we have a MEM.  gen_highpart must return a valid operand,

>>> -     emitting code if necessary to do so.  */

>>> -  if (MEM_P (result))

>>> +  /* gen_lowpart_common handles a lot of special cases due to needing to handle

>>> +     paradoxical subregs; it only calls simplify_gen_subreg when certain that

>>> +     it will produce something meaningful.  The only case we need to handle

>>> +     specially here is MEM.  */

>>> +  if (MEM_P (x))

>>>       {

>>> -      result = validize_mem (result);

>>> -      gcc_assert (result);

>>> +      poly_int64 offset = subreg_highpart_offset (mode, GET_MODE (x));

>>> +      return adjust_address (x, mode, offset);

>>>       }

>>>   

>>> +  result = simplify_gen_subreg (mode, x, GET_MODE (x),

>>> +				subreg_highpart_offset (mode, GET_MODE (x)));

>>> +  /* Since we handle MEM directly above, we should never get a MEM back

>>> +     from simplify_gen_subreg.  */

>>> +  gcc_assert (result && !MEM_P (result));

>>> +

>>>     return result;

>>>   }

>>>

Patch

diff --git a/gcc/emit-rtl.c b/gcc/emit-rtl.c
index 77ea8948ee8..0ba110879aa 100644
--- a/gcc/emit-rtl.c
+++ b/gcc/emit-rtl.c
@@ -1585,19 +1585,22 @@  gen_highpart (machine_mode mode, rtx x)
   gcc_assert (known_le (msize, (unsigned int) UNITS_PER_WORD)
 	      || known_eq (msize, GET_MODE_UNIT_SIZE (GET_MODE (x))));
 
-  result = simplify_gen_subreg (mode, x, GET_MODE (x),
-				subreg_highpart_offset (mode, GET_MODE (x)));
-  gcc_assert (result);
-
-  /* simplify_gen_subreg is not guaranteed to return a valid operand for
-     the target if we have a MEM.  gen_highpart must return a valid operand,
-     emitting code if necessary to do so.  */
-  if (MEM_P (result))
+  /* gen_lowpart_common handles a lot of special cases due to needing to handle
+     paradoxical subregs; it only calls simplify_gen_subreg when certain that
+     it will produce something meaningful.  The only case we need to handle
+     specially here is MEM.  */
+  if (MEM_P (x))
     {
-      result = validize_mem (result);
-      gcc_assert (result);
+      poly_int64 offset = subreg_highpart_offset (mode, GET_MODE (x));
+      return adjust_address (x, mode, offset);
     }
 
+  result = simplify_gen_subreg (mode, x, GET_MODE (x),
+				subreg_highpart_offset (mode, GET_MODE (x)));
+  /* Since we handle MEM directly above, we should never get a MEM back
+     from simplify_gen_subreg.  */
+  gcc_assert (result && !MEM_P (result));
+
   return result;
 }